Cathode unit



March 31, 1970 N. A. lOFlS ETAL 3,504,220

QATHODE UNIT Filed Sept. 14, 1967 v United States Patent US. Cl. 313-2703 Claims ABSTRACT OF THE DISCLOSURE A cathode unit for electrical vacuuminstruments comprises a cathode with a preheater in respective parts ofa ceramic insulator which include projections and slots to define heatand current insulative gaps between the regions where the cathode andpreheater are secured.

The present invention relates to cathode units used in electric vacuuminstruments.

There are known cathode units for electric vacuum instruments comprisinga cathode, a preheater and an insulator wherein the cathode and thepreheater are secured on one insulator (cf. Hungarian Patents Nos.143,842 and 144,743).

A disadvantage of these constructions lies in current leakage in thecathode-preheater circuit which restricts the field of their applicationto only those instruments wherein the cathode is electrically connectedto the preheater.

Another disadvantage of the known constructions of the above type whenused ior electronic instruments is their high thermal conductivity.

An object of the present invention is to eliminate these disadvantages.

Another object of the present invention is to provide a cathode unit forelectronic instruments wherein current leakage in the preheater-cathodecircuit is eliminated and insulator thermal conductivity issubstantially reduced.

These and other objects are achieved in a cathode unit with a cathodeand a preheater secured on an insulator wherein, according to theinvention, a gap is provided between the areas intended for securing thecathode and the preheater on the insulator.

One of the possible embodiments of the invention is a cathode unit withan insulator made of two parts, one of which serves for securing thepreheater, while the other serves for securing a cathode. The insulatorparts are provided with slots and projections which, when the insulatoris assembled, form a gap between the parts. Said parts are connectedbeyond the cathode and preheater attachment areas prior to mounting thecathode and the preheater.

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Hereinbelow is given a detailed description of an exemplary embodimentof a cathode unit according to the invention in conjunction with theaccompanying drawing, wherein:

FIG. 1 is a sectional view of the cathode unit;

FIGS. 2 and 3 show parts of the cathode unit insulator; and

FIG. 4 illustrates a cathode unit insulator assembly.

The butt-type cathode unit consists of a cathode 1 (FIG. 1) and apreheater 2, secured in a ceramic insulator 3 made of two parts 4 and 5,the preheater 2 being secured in part 4 of a greater diameter, and thecathode 1 being secured in part 5 of a smaller diameter.

The parts are provided with respective slots 6 and projections 7 which,when assembled, form a gap 8 between the parts 4 and 5.

The attachment places of the parts 4 and 5 are outsidethe area intendedfor securing the cathode and the preheater in the insulator.

The parts are connected according to the well-known manufacturing method(by sintering) prior to assembling the cathode unit.

Such embodiment of the cathode unit ensures separation of the areaswhere the cathode 1 (FIG. 1) and the preheater 2 are secured.

What we claim is:

1. A cathode unit for electric vacuum instruments comprising a cathode,a preheater, an insulator, means securing said cathode and preheater onsaid insulator in specific regions thereof, and means defining heat andcurrent insulative gaps in said insulator in the regions where saidcathode and said preheater are secured to said insulator.

2. A cathode unit according to claim 1 in which the insulator comprisestwo parts respectively mounting said preheater and said cathode, saidparts having respective projections and slots which constitute the meansdefining said gaps.

3. A cathode unit according to claim 2 wherein said cathode is engagedin said projections and said preheater is mounted within the cathode andsecured in the part having the slots for receiving the projections.

References Cited UNITED STATES PATENTS 3,311,774 3/1967 Atti 3l3337 XJOHN W. HUCKERT, Primary Examiner R. F. POLISSACK, Assistant ExaminerUS. Cl. X.R.

